Determination of surgical exposure obtained with integrated endoscopic thoracolumbar hemilaminectomy in large-breed cadaveric dogs

Objective To define boundaries of minimally invasive integrated endoscopic hemilaminectomy at 4 sites in the canine thoracolumbar spine. Study design Experimental, randomized cadaveric study. Animals Six cadaver dogs that had been humanely euthanized for reasons unrelated to this study. Methods Hemilaminectomy was performed with an integrated endoscopic system at T11-12, T12-13, L1-2, and L2-3, 1 at each site, on the left or right side of each dog. Each site was randomly assigned either a 19-mm or a 23-mm cannula. The entire procedure, including soft tissue dissection, was performed through the cannula. Afterward, spines were imaged by computed tomography (CT) to measure the cranial and caudal extent of the hemilaminectomy from the center of the disc space. Results The mean +/- SD cranial extent of the hemilaminectomy was 4.5 +/- 1.4 mm for the 19-mm cannula and 5.6 +/- 1.4 mm for the 23-mm cannulas (P = .0757). The caudal extent of the hemilaminectomy was 9.5 +/- 2.2 mm for the 19-mm cannula and 10.3 +/- 1.6 mm for the 23-mm cannula (P = .206). The mean length of the hemilaminectomy was 13.0 +/- 1.5 mm for the 19-mm cannula and 15.0 +/- 2.1 mm for the 23-mm cannula (P = .022). Conclusion Integrated endoscopic systems were reliably used to access the spinal canal within the range of the above measurements relative to the disc space as identified by CT or magnetic resonance imaging. Clinical significance Integrated endoscopy can be considered as an option in dogs with thoracolumbar disc extrusions or other pathology measuring within the parameters defined by this study. Access may be possible beyond the dimensions defined in this study with probing and repositioning.